This invention relates generally to an apparatus for use in high tension electrical transmission line maintenance and, more particularly, to an apparatus for replacing the electrical insulators used in such high tension lines.
High tension electrical transmission lines are supported above ground by a variety of support structures made of steel, wood, cement or the like. The electrical lines are typically connected to the support structure by a plurality of electrical insulators connected together in string fashion. The string of insulators supports the weight of the transmission lines and, as such, are under considerable tension. It is known, for example, that the tension in such transmission lines can vary widely depending upon the length of the line, etc., but is typically in the order of 485-36,000 lbs. Due to this considerable line tension, the procedure for replacing electrical insulators that have been damaged by lightening or malicious mischief, such as firearm discharge, is a complicated procedure. The replacement of damaged insulators is a regular occurrence in transmission line maintenance and is essential to prevent unnecessary power outages caused by flashovers.
The typical procedure for replacing damaged insulators was a lengthy, costly process requiring an insulator cradle, gin poles and other complex and cumbersome equipment. The transmission lines are de-energized for this process, at a cost in the order of $25,000 per hour of down-time. Thus, there is a great need for a procedure which reduces the time required to replace the insulators and, thus, the down-time for the line.
In U.S. Pat. No. 1,997,109 to Fyfe, one type of apparatus for replacing damaged insulators is disclosed. This apparatus, however, suffers from several disadvantages in a structural and operational sense. One such disadvantage is that the apparatus is comprised of multiple pieces which must be assembled around the string of insulators. That is, the apparatus is incapable of being assembled prior to application around the insulators. Moreover, because it is a multiple piece apparatus, it is time-consuming and difficult to assemble and increases the risk of a lineman dropping one of the pieces while suspended above ground.
Another disadvantage of the Fyfe apparatus is that it applies tension to the porcelain disk of the insulator. Typically, the insulators needed to be replaced have damaged disk portions and, in any event, the porcelain disk is not strong enough to support the degree of tension required to be applied to replace present day insulators.
Furthermore, the Fyfe apparatus was designed for use with insulators having a mortise and tenon connection and would not be expected to be applicable to the present day ball-and-socket insulators. In addition, the Fyfe apparatus does not have any safety features to prevent the insulators from slipping out of the apparatus while the insulators were being replaced.
I have invented a very simple insulator-jack which eliminates the need for complex, cumbersome equipment and greatly expedites the procedure for replacing insulators, and which can be assembled prior to application and which is faster and easier to operate than equipment heretofor known.